1. Field of the Invention
The present invention relates to an automatic original feeder for use in an image scanner or an image forming device.
2. Description of the Related Art
Some automatic original feeders include a separating and feeding unit that includes a comb tooth-like feed roller and a comb tooth-like separation roller. A plurality of convex portions that protrude in a diameter direction of the roller shaft of the feed roller are formed on the surface of the feed roller at predetermined intervals. The feed roller rotates in a direction of feeding of an original. A plurality of convex portions that protrudes in a diameter direction of the roller shaft of the separation roller are formed on the surface of the separation roller at predetermined intervals. The separation roller rotates in an opposite direction to the direction of feeding of the original. The feed roller and the separation roller are positioned such that their convex portions get engaged with each other. The amount for which the feed roller and the separation roller engage with each other is called the engagement amount. As the feed roller and the separation roller rotate, they pickup an original from a stack of originals. A conventional technique has been disclosed in, for example, Japanese Patent Application Laid-Open No. 11-322105.
It is common to make the roller shaft of the separation roller from resin instead of iron or stainless steel, because resin has higher elasticity than iron or stainless steel.
However, in the conventional automatic original feeders, the engagement amount is fixed, so that originals with thickness or quality in a certain range can only go well with them. In other words, there is a restriction on the original that can be used.